small soldering iron. I recommend soldering one pad on
each diode and then inspecting it with a magnifier to
make sure the dots are correct. It’s easy to remove one if
reversed. However, if both sides are soldered you almost
need a surface-mount removal soldering iron. Perform the
same procedure using the LEDs.
Solder the power jack and the .01 µF cap to the
board. If you want to use batteries, there is a mounting
hole for the wire and pads for soldering. Solder in the DIP
switch.
Next, solder the microcontroller, two 470 ohm
networks, and the SIP. The SIP sets the sensitivity of the
target for ambient light. I found 3.3K worked best. The
higher the resistance, the more sensitive the target
becomes to light. Please note that the square pads
indicate pin 1 (watch the SIP
position). Solder the three PNP
transistors (flat side points to the
top), the three 10K 1/8 watt
resistors, and the reset switch.
Solder the six headers. The
microcontroller can be
programmed on the board using
the six-pin header and a Microchip
PICKIT 2 available in the Nuts &
Volts webstore at
www.nutsvolts.com.
The programming files are also
located on the Nuts & Volts
website, along with all the
necessary files to complete this
project.
■ FIGURE 4.
BILL OF MATERIALS
ITEM DESCRIPTION QTY MANUFACTURER/PART
Microchip/PIC16F917-I/P
Eagle/12BH348/CS-GR
dots. You can use fine solder but I found it was easier to
use a solder paste. Put one small dab on each pad (don’t
use too much). Using curved forceps, pick up a
photodiode and place it on the pad. Touch the pad with a
TARGET:
IC1
Battery Holder
PCB*
C1
Header
Microcontroller 1
Jack
LEDs
Photodiodes
Q1-3
R1-6
R9
CUI/PJ-102A
Kingbright/AP201SRCPRV
Everlight/EL-PT11-21C/41TR8
C&K/PVA1 EE H2
Testing the Target
Lite-on-Inc /LTC-4624JR
6-32 x 1/2”
4”x 4” x 3/16”
4”x 4” .01 mm frosted
1/4”
PHOTON EMITTER:
IC1 Microcontroller
PCB* 1
1
Microchip/PIC12F508-1/SN
Laser
LPT
Microphone
1545P-R
R1-2
1
1
Quarton, Inc./VLM-650-03-
2.2K ohm x 4 mm
1
Project Unlimited/TOM-
10 K 805 Surface-mount
Microswitch
Miscellaneous:
Batteries
Brass Washer
Plastic Rod
Set Screws
Set Screw
2
1
Copal Electronics/CHS-01TB
To test the board, I use a laser
pointer. Connect the power and
turn on the target. A bar should be
displayed indicating that the power
is on. Set the DIP switch on test.
Press the reset switch. Using a
laser, light one of the four diodes
in column one, row one. Each hit
on the diode will flash the LED in
the center. Perform this procedure
in each of the 49 squares, testing
all 196 photodiodes. This test is to
make sure all the photodiodes and
LEDs have been properly installed.
#10 hearing aid 5
#4 1
3” length 5/8” diameter 1
4-40 1/8” 3
1/4-20 3/8” 1
Final Assembly
*Printed Circuit Boards and programming chips are available in the
Nuts & Volts webstore ( www.nutsvolts.com).
All parts can be obtained through www.mouser.com or www.digikey.com.
The target can be printed on
styrene using a laser printer. (The
target diagram is in a Word
document on the Nuts & Volts
website.) Make another copy on
32
May 2010
